FORWARD AND INVERSE MODELING ALONG A FLOW PATH WITHIN CONSTRUCTED WETLANDS DESIGNED TO TREAT LANDFILL LEACHATE

Forward and Inverse Modeling Along a Flow Path Within Constructed Wetlands Designed to Treat Landfill Leachate

Kristen Andrews and Eung Seok Lee

Landfill leachate poses a significant environmental threat due to its high pollutant load and potential for ground and surface water contamination. Characterization of leachate is important as it evolves and depends on the type of landfill, landfill construction, and the stage of decomposition of the landfill contents. Leachate must be treated before it is released back into the environment to minimize pollutant load levels, not to exceed maximums set by state environmental regulatory agencies. This study focused on characterizing and assessing the treatment efficiency of a six-cell constructed wetland at the Athens County 691 Landfill in Ohio by delineating chemical evolution along the flow path through analyses of historical and current water quality data and geochemical modeling using PHREEQCI. Field results obtained to date have shown increased removal efficiency at lower ambient air temperatures. Oxidation-reduction potential exhibited improved recovery, pH was mitigated more effectively, and total dissolved solids removed at increased levels. ORP levels in influent were -113 mV and 2 mV at the effluent, pH saw an increase from 6.48 to 7.69, and TDS went down from 933.1 mg/L to 522.5 mg/L. Combining water quality field data and modeling results, a broader understanding of the wetland's performance was obtained and strategies for enhancing the treatment efficiencies were suggested. Enhanced performance of constructed wetlands can further lower costs and help protect water resources and human health.